Arrangements comprising integrated circuits of the type described above are found today in almost all articles of daily use comprising integrated electronics. Devices for electronic data processing, communication or for recording data have provisions which restrict the read, write or modification access to the data depending on the type of data processed. This is intended to protect data against public accessibility or manipulation. It is particularly in the field of the future generation of tachographs, the digital tachograph, that protection of recorded data against manipulation is of the highest significance.
Previous manipulation-protected systems with high security requirements normally consist of a number of discrete assemblies to which different functions are allocated, for example a central processing unit, an encryption unit and various memories are in each case normally an independent unit which is connected to the other units. The requirement of having a number of assemblies and assembling them and matching them to one another is associated with high costs in the series production.